Archive for August, 2012

“’Tis now the very witching time of night, When churchyards yawn and hell itself breathes out Contagion to this world”

–William Shakespeare

Yawning is very much on my mind today, as I settle in to write the last blog entry in this particular series.  I recently decreased my caffeine intake, from four large cups in the morning and several sodas or cups of coffee during the day to two large cups of coffee in the morning.  Two things inspired the change.  First, I was beginning to have a lot of difficulty falling asleep, and would often find myself awake at 4am with a morning class looming on the horizon. Since I am not a morning person, this became increasingly uncomfortable, not to mention all that yawning (sometimes in the middle of lecturing!).

Secondly, I discovered the wonders of French press coffee by whim shopping online one night when I couldn’t sleep.  Yes, the irony that I bought something to keep me awake one night when I couldn’t sleep was not lost on me. The French press I bought was a 32oz pot, which is two cups worth in my favorite coffee mug.  I can’t begin to describe how delicious French press coffee is—I can’t drink coffee any other way now.  Of course, I could just buy a bigger French press, but I figured it was good way to motivate myself to cut down.  It seems to have worked, since my sleeping patterns have normalized, and I have less trouble falling asleep when I go to bed.

The other reason yawning is on my mind today, in particular, is due to a text message from a friend who is a morning person who doesn’t realize that not everyone is awake at 7am when there are no classes in session.   So I’ve been yawning up a storm today, despite trying to keep my mouth closed and breathing through my nose (which really does work to decrease the frequency of yawning; I’ve been informally tracking that all summer in myself).

For this last entry, I want to take a look at yawning as a symptom.  Yawning is a seemingly simple behavior, though as we have learned over the last several weeks  it is a complex and little-understood behavior.  All humans, as far as we know, yawn, and we all yawn in the same, stereotypical way.  Even people who are profoundly paralyzed and can barely move a muscle still yawn (though not contagiously) as well as people who have had everything but their brainstem removed (Provine, 2005).  Interestingly, Cattaneo, Cucrachi, Chierici, and Pavesi (2006) document two patients who suffered strokes in their brainstem who developed excessive yawning as a result, further suggesting that the control of yawning is located in the brainstem and medulla.

Changes in yawning frequency are also associated with certain medications, particularly SSRIs, which are used to treat anxiety and depression.  Taskapilioglu, Akkaya, Sarandol, and Kirli (2009) documented the case of a female patient who began to yawn excessively while taking an SSRI for anxiety.  Other researchers have noted excessive yawning for patients taking SSRIs (Chen and Lu, 2009; Gutiérrez-Álvarez, 2007).  Beale and Murphree (2000) took a closer look at this side-effect in two case studies for individuals being treated for major depression using SSRI’s fluoxetine and sertraline, among other medications.  Both developed excessive yawning within 14 days of the start of treatment.  In one of the cases, the excessive yawning continued across three SSRIs and only went away when the medication was discontinued.  Yawning is such a notorious side effect of the drug Lexapro that the symptom is often referred to as The Lexapro Yawn.

Daquin, Micallef, and Blin (2001) provide a nicely detailed overview of various other pathologies that are associated with excessive yawning.  The disorders cover a broad spectrum of categories, and include neurological and psychiatric pathologies as well as physiological, infectious, and metabolic.  Lets take a look at some of the pathologies associated with central nervous system disorders.  People who suffer from migraines often experience yawning before, during, or after an attack.  Research has indicated that people who suffer from migraines may have a hyper-sensitive dopaminergic system.  We learned in an earlier blog entry that dopamine plays a role in yawning as well, with yawning often triggered in humans and animals by the administration of a dopamine agonist, such as apomorphine.  As an added bit of evidence, people who have Parkinson’s Disease tend to yawn much less frequently than normal, due in part to the dopamine deficiency that is a hallmark of the disorder.  Given that dopamine levels in the brain are also related to schizophrenia, yawning is often seen as a symptom in that disorder as well.

As I mentioned earlier, in the blog post about causes of yawning, I think neurotransmitter regulation, or at least neurotransmitter levels, is the place to look for causes.  There is a very long list of neurotransmitters associated with yawning, particularly dopamine and serotonin, and the appearance of excessive yawning as a side effect in many disorders, either as a natural part of the disorder or as a result of medication seem to support the idea.  I’ve really enjoyed reading and writing about yawning, and haven’t even really scratched the surface of the phenomenon.  I will probably update this blog on yawning research as I come across it in the future.

To close out this round of blogging, I’d like to thank my students in the Summer II 2012 session of PSY 229 Introduction to Biological Psychology at Cedar Crest College, who have been blogging on a variety of topics along with me.  It’s been fascinating to read your blogs on many levels for me.  Since this is an online class it’s hard for us to get to know each other.  Your blogs have told me a lot about who you are as people and what you find interesting about brain and behavior.  I appreciate all your hard work on this assignment, as well as your insight and research that you have all so enthusiastically shared with each other.  I hope you have found the assignment as enjoyable as I have, not only in terms of sharing your interest and knowledge, but also reading the blog posts of your fellow students.  I especially hope that some of you will continue the practice of blogging, if not necessarily about brain and behavior, at least about those things you find especially interesting as you continue your education.  Writing about something is a tremendously beneficial scholarly activity and I encourage all of you to do it regularly.  You will not regret it.


Beale, M. D., & Murphree, T. M. (2000). Excessive yawning and SSRI therapy. International Journal Of Neuropsychopharmacology, 3(3), 275-276. doi:10.1017/S1461145700001966

Cattaneo, L. L., Cucurachi, L. L., Chierici, E. E., & Pavesi, G. G. (2006). Pathological yawning as a presenting symptom of brain stem ischaemia in two patients. Journal Of Neurology, Neurosurgery & Psychiatry, 77(1), 98-100. doi:10.1136/jnnp.2005.075267

Chen, C., & Lu, M. (2009). Venlafaxine-induced excessive yawning. Progress In Neuro-Psychopharmacology & Biological Psychiatry, 33(1), 156-157. doi:10.1016/j.pnpbp.2008.10.014

Daquin, G., Micallef, J., & Blin, O. (2001). Yawning.  Sleep Medicine Review, 5(4), 299-312. doi:10.1053/smrv.2001.0175

Gutiérrez-Álvarez, Á. M. (2007). Do your patients suffer from excessive yawning?. Acta Psychiatrica Scandinavica, 115(1), 80-82. doi:10.1111/j.1600-0447.2006.00856.x

Provine, R. R. (2005).  Yawning.  American Scientist, 93(6), 532-539 doi: 10.1511/2005.56.980.

Taskapilioglu, O. O., Akkaya, C. C., Sarandol, A. A., & Kirli, S. S. (2009). Pathological yawning in a patient with anxiety and chronic disease anaemia. Journal Of Psychopharmacology, 23(2), 211-213. doi:10.1177/0269881108089812


A yawn is more disconcerting than a contradiction.

One major category of theories about why we yawn focus on the idea of regulation.  That is, yawning could provide the body with some significant resource that has become depleted over time, returning it to an appropriate level to ensure optimal functioning.  In an earlier blog post, I described the three phases of yawning:  an active inhalation, the acme, and a rapid expulsion of air, with the entire process lasting about six seconds.  Barbizet (1958) provides much more detail about the physiology of yawning, which includes increasing the size of the airways and lowering the diaphragm, all designed to bring in a significant influx of air.

The air we breathe is composed of about 78% nitrogen, 21% oxygen, 1% argon, and less than 0.05% carbon dioxide, as well as other molecules and water vapor (about 1%). Oxygen is the key ingredient here; our physiological systems evolved to use oxygen in many cellular activities, particularly the absorption of nutrients.  Blood oxygen levels are very important, and oxygen starvation, also known as hypoxia, can cause significant damage and can even be fatal.

It should come as no surprise, then, that one theory of yawning states that we do so to increase the amount of oxygen in our blood.  Another related theory states that we might yawn because CO2 levels in our blood are too high and yawning is a way to reduce those levels.  To test this Provine, Tate, and Geldmacher (1987) measured yawning rates in college students under either high levels of oxygen (which should significantly decrease the frequency of yawning) or higher-than-normal intake of CO2 (which should significantly increase the frequency of yawning).  In both cases, the rate of yawning was unaffected and they concluded that yawning does not serve a regulatory function with respect to respiration, and that it was likely triggered by other internal factors.  Other researchers have reached the same conclusion.

We know that the frequency of yawning is the highest when we are sleepy, such as when we first wake up or when we are getting ready to go to bed.  In fact, Zilli, Giganti, and Salzarulo, (2007) were able to show that the temporal distribution of yawning differed between morning and night people (i.e. those who feel they function best at a particular time of day, be it early morning or late at night.).  It also occurs when a tedious task bores us and makes us feel sleepy.  This has led some to hypothesize that yawning is a way of producing arousal and increasing vigilance.  Guggisberg, Mathis, Herrmann and Hess, (2007) measured changes in heart rate and electrical brain activity in sleepy participants who were spontaneously yawning.  They found that yawning was definitely associated with sleepiness, but was not associated with significant increases in autonomic arousal.

A newer regulatory theory has surfaced recently, though it is hotly debated (pun intended), and that is that yawning cools the brain.  Gallup and Gallup (2007) measured significant increases in the frequency of contagious yawning when warm packs where held to the foreheads of participants.  They also found a significant decrease in the number of yawns for participants who held a cool pack to their foreheads.  The authors claim that the cold packs cool the blood in the vessels of the face, which leads to cooling of the brain.  Some researchers, including Elo (2011) dispute this claim, citing little or no empirical evidence to support the notion that ice packs can significantly cool the brain quickly enough.  This theory, which has gained some traction in the popular press, continues to be debated among researchers.

It seems, then, that we are no closer to understanding the reasons for why we yawn than we were decades ago when people first began systematically researching the question.  No clear and definitive answer has yet been produced by empirical research to support any given theory.  Guggisberg, Mathis, Schnider, and Hess (2011) point out that none of the studies to date examining theorized physiological regulatory functions for yawning have produced any clear links between yawning and physiology, and add that the only demonstrably specific effect of yawning is that it is contagious in some species, including humans.  While this is not clear evidence for the communicative function of yawning (which I talked about in my previous blog post), it is interesting that this is the major finding to date.

So yawning remains an enigma, a common behavior across many species, one that we all have experienced and probably given little thought to except when yawning is persistent and disruptive.  To my knowledge there is no documented case of a person or organism that should yawn, but never does.  If anyone finds such a case, please let me know.

One area I shall have to spend some more time looking into, I think, is the link between neurotransmitters and yawning.  I mentioned in an earlier blog post that a significant number of neurotransmitters are involved in yawning, but I only listed a fraction of them.  Since yawning is clearly linked to sleepiness, appears to serve some communicative function, and is clearly tied to neurotransmitter activity, I think that’s the place to look for an explanation, though I can’t even begin to imagine what that might be.  It just seems like the obvious place.  I also suspect that yawning may be the beginning or end of a cascade of events all put into motion by a particular trigger, be that trigger physiological or social.  If that’s the case, it’s no surprise that we can’t find a single cause.  It could be that yawning is a single cog in a complicated mechanism involving many systems, all working together in a particular way, rather than a single cause and effect relationship between some physiological mechanism, such as blood oxygen level or brain temperature, and yawning.

Next week:  Yawning and pathology


Barbizet, J. (1958).  Yawning.  Journal of Neurology, Neurosurgery & Psychiatry.  21203-209 doi: 10.1136/jnnp.21.3.203

Elo, H. (2011). Yawning cannot cause significant temperature decreases in humans. Sleep Medicine, 12(1), doi:10.1016/j.sleep.2010.06.005

Gallup, A.C., and Gallup, G.R. (2007). Yawning as a brain cooling mechanism: Nasal breathing and forehead cooling diminish the incidence of contagious yawning.  Evolutionary Psychology, 5(1). 92-101.

Guggisberg, A. G., Mathis, J., Herrmann, U. S., & Hess, C. W. (2007). The functional relationship between yawning and vigilance. Behavioural Brain Research, 179(1), 159-166. doi:10.1016/j.bbr.2007.01.027

Guggisberg, A. G., Mathis, J., Schnider, A., & Hess, C. W. (2011). Why do we yawn? The importance of evidence for specific yawn-induced effects. Neuroscience And Biobehavioral Reviews, 35(5), 1302-1304. doi:10.1016/j.neubiorev.2010.12.004

Provine, R.R., Tate, B.C., and Geldmacher, L.L. (1987).  Yawning:  No effect of 3-5% CO2, 100% O2, and exercise.  Behavioral and Neural Biology, 48(3), 382-393.

Zilli, I., Giganti, F., & Salzarulo, P. (2007). Yawning in morning and evening types. Physiology & Behavior, 91(2-3), 218-222. doi:10.1016/j.physbeh.2007.02.015